47 research outputs found
Remotely Readable Fiber Optic Compass
PatentA remotely readable fiber optic compass. A sheet polarizer
is affixed to a magnet rotatably mounted in a compass
body, such that the polarizer rotates with the magnet.
The optical axis of the sheet polarizer is preferably
aligned with the north-south axis of the magnet. A single
excitation light beam is divided into four identical
beams, two of which are passed through the sheet polarizer
and through two fixed polarizing sheets which have
their optical axes at right angles to one another. The
angle of the compass magnet with respect to a fixed axis
of the compass body can be determined by measuring
the ratio of the intensities of the two light beams. The
remaining ambiguity as to which of the four possible
quadrants the magnet is pointing to is resolved by the
second pair of light beams, which are passed through
the sheet polarizer at positions which are transected by
two semicircular opaque strips formed on the sheet
polarizer. The incoming excitation beam and the four
return beams are communicated by means of optical
fibers, giving a remotely readable compass which has
no electrical parts
New and Improved Diagnostics for Detection of Drug-Resistant Pulmonary Tuberculosis.
PURPOSE OF REVIEW: Tuberculosis (TB) remains a global emergency and continues to kill 1.7 million people globally each year. Drug-resistant TB is now well established throughout the world and most TB patients are not being screened for drug resistance due to lack of laboratory resources and rapid accurate point-of-care tests. Accurate and rapid diagnosis of TB and drug-resistant TB is of paramount importance in establishing appropriate clinical management and infection control measures. During the past decade, there have been significant advances in diagnostic technologies for TB and drug-resistant TB. The purpose of this article is to review the current data, recommendations and evidence base for these tests. RECENT FINDINGS: Second-line drug susceptibility testing (DST) is complex and expensive. Automated liquid culture systems and molecular line probe assays are recommended by the WHO as the current 'gold standard' for first-line DST. Liquid culture DST for aminoglycosides, polypeptides and fluoroquinolones has been shown to have relatively good reliability and reproducibility for diagnosis of extensively drug-resistant TB; however, DST for other second-line drugs (ethionamide, prothionamide, cycloserine, terizidone, para-aminosalicylic acid, clofazimine, amoxicillin-clavulanate, clarithromycin, linezolid) is not recommended. Automated liquid culture systems are currently recommended by the WHO as the 'gold standard' for second-line DST. SUMMARY: In this review, we describe the phenotypic and genotypic methods currently available for the diagnosis of TB and drug-resistant forms of Mycobacterium tuberculosis and discuss future prospects for TB diagnostics. Current technologies for the detection of drug resistant M. tuberculosis vary greatly in terms of turnaround time, cost and complexity. Ultimately, the 'holy grail' diagnostic for TB must fulfil all technical specifications for a good point-of-care test, screen for drug resistance concurrently and be adaptable to the various health system levels and to countries with diverse economic status and TB burden. © 2011 Lippincott Williams & Wilkins, Inc
Bounding the pseudogap with a line of phase transitions in YBCO cuprate superconductors
Close to optimal doping, the copper oxide superconductors show 'strange
metal' behavior, suggestive of strong fluctuations associated with a quantum
critical point. Such a critical point requires a line of classical phase
transitions terminating at zero temperature near optimal doping inside the
superconducting 'dome'. The underdoped region of the temperature-doping phase
diagram from which superconductivity emerges is referred to as the 'pseudogap'
because evidence exists for partial gapping of the conduction electrons, but so
far there is no compelling thermodynamic evidence as to whether the pseudogap
is a distinct phase or a continuous evolution of physical properties on
cooling. Here we report that the pseudogap in YBCO cuprate superconductors is a
distinct phase, bounded by a line of phase transitions. The doping dependence
of this line is such that it terminates at zero temperature inside the
superconducting dome. From this we conclude that quantum criticality drives the
strange metallic behavior and therefore superconductivity in the cuprates
Origin of the X-rays and Possible GeV-TeV Emission from the Western Hot Spot Of Pictor A
Pictor A is a nearby Fanaroff-Riley class II (FR II) radio galaxy with a
bright hot spot, the western hot spot. Observation of high polarization in the
optical emission of the hot spot indicates that the optical emission could be
synchrotron radiation of relativistic electrons in the hot spot. These
electrons may be able to produce high energy gamma-ray photons through inverse
Compton (IC) scattering. We use single-zone and multi-zone synchrotron +
synchrotron-self-Compton (SSC) models to fit the observed spectral energy
distribution (SED) from the radio to the X-ray band of the hot spot. Our esults
show that in the case of a much weaker magnetic field strength than the
equipartition magnetic field, both the single-zone and multi-zone models can
fit the SED, but the multi-zone model significantly improves the fit. The two
models predict the hot spot as a GeV-TeV source, which might be marginally
detectable with Fermi/LAT and HESS. The inverse Compton scattering of cosmic
microwave background (IC/CMB) is also considered, but its contribution to
GeV-TeV emission is negligible. Note that under the equipartition condition,
the SED can also be fit with the multi-zone model, but the predicted flux at
10^22 Hz is too weak to be detectable. The detection of TeV gamma-rays from
this FR II radio galaxy, if confirmed, would establish a new subclass of
extragalactic source in this energy regime since most of the AGNs detected to
date at TeV energies are high-energy-peaked BL Lac objects.Comment: 15 pages, 3 figures, accepted for publication in Ap
Comparative High Field Magneto-Transport of Rare Earth Oxypnictides with Maximum Transition Temperatures
The recent discovery of a new class of superconducting oxypnictides with high
transition temperatures may have profound implications for understanding
unconventional high-temperature superconductivity. Like the cuprates, the
oxypnictides seem to manifest an interleaving of charge donor and
superconducting layers emerging upon doping of an antiferromagnetic parent
semi-metal. Here we report magneto-transport measurements of three rare earth
(Re = La, Nd, Sm) oxypnicide compounds with the transition temperatures near
the maximum reported to date, in very high DC and pulsed magnetic fields up to
45 and 54 T, respectively. Our resistivity, Hall coefficient and critical
magnetic fields data suggest that these oxypnictide superconductors bridge the
gap between MgB and YBaCuO as far as electromagnetic and vortex
properties are concerned.Comment: 6 pages, 3 figure
Blazars as Ultra-High-Energy Cosmic-Ray Sources: Implications for TeV Gamma-Ray Observations
The spectra of BL Lac objects and Fanaroff-Riley I radio galaxies are
commonly explained by the one-zone leptonic synchrotron self-Compton (SSC)
model. Spectral modeling of correlated multiwavelength data gives the comoving
magnetic field strength, the bulk outflow Lorentz factor and the emission
region size. Assuming the validity of the SSC model, the Hillas condition shows
that only in rare cases can such sources accelerate protons to much above 10^19
eV, so > 10^20 eV ultra-high-energy cosmic rays (UHECRs) are likely to be heavy
ions if powered by this type of radio-loud active galactic nuclei (AGN).
Survival of nuclei is shown to be possible in TeV BL Lacs and misaligned
counterparts with weak photohadronic emissions. Another signature of hadronic
production is intergalactic UHECR-induced cascade emission, which is an
alternative explanation of the TeV spectra of some extreme non-variable blazars
such as 1ES 0229+200 or 1ES 1101-232. We study this kind of cascade signal,
taking into account effects of the structured extragalactic magnetic fields in
which the sources should be embedded. We demonstrate the importance of
cosmic-ray deflections on the gamma-ray flux, and show that required absolute
cosmic-ray luminosities are larger than the average UHECR luminosity inferred
from UHECR observations and can even be comparable to the Eddington luminosity
of supermassive black holes. Future TeV gamma-ray observations using the
Cherenkov Telescope Array and the High Altitude Water Cherenkov detector array
can test for UHECR acceleration by observing >25 TeV photons from relatively
low-redshift sources such as 1ES 0229+200, and > TeV photons from more distant
radio-loud AGN.Comment: 14 pages, 9 figures, 2 tables, accepted for publication in ApJ,
references and discussions adde